Two British Columbia basins may be opened for exploration

June 26, 2000
British Columbia has proposed to open two new land basins for oil and gas exploration.

British Columbia has proposed to open two new land basins for oil and gas exploration.

Discussions are at a very early stage, but Provincial Minister of Energy and Mining Dan Miller said he will begin consulting with the communities of Prince Rupert and Prince George on possible development in the region.

The Bowser and Nechako basins are believed to have significant oil and gas potential. A number of companies have expressed interest, but none has made formal application, the energy and mining ministry said.

Surface area of the two basins combined is about two-thirds that of the 142,000-sq-km portion of the Western Canada Sedimentary basin in Northeast BC that provides 100% of the province's gas and oil production.

Miller also said some consultation is occurring on possible exploration in the Hecate strait between the mainland and the Queen Charlotte Islands (OGJ, Aug. 24, 1992, p. 53). The offshore area is under a moratorium, and the minister said that any plans for offshore development will be approached very carefully in the environmentally-sensitive region.

Bowser, Nechako update

Unpublished data from Geological Survey of Canada that make up the bulk of this article show resource assessments and the minimum drilling that has taken place in the two basins.

Nechako has only 12 wells dating from the 1930s to the late 1970s and early 1980s, six of which Canadian Hunter Exploration Ltd. drilled in 1980-86.

Two wells were drilled in the Bowser basin, in 1969 and 1973.

The Bowser and Nechako basins are the two largest of eight large and small intermontaine sedimentary basins and troughs found in the interior of British Columbia. The several basins stretch from Yukon Territory to Washington State.

The Bowser basin covers 57,000 sq km including the immediately adjacent Sustut basin, and the Nechako basin area is 69,000 square km.

Bowser's two exploratory wells are near the basin's western edge. Dome Petroleum Ltd. drilled the wells to depths of 6,932 ft and 9,700 ft.

Well records indicate that the first well penetrated Jurassic and Triassic shales and sands throughout, and note is made that a mud-gas detector recorded gas from fractured shales at about 6,000 ft. The deeper well also spudded in Jurassic shales and penetrated 9,000 ft of shales, sands, and conglomerates until encountering volcanics from 9,155 ft to TD. No other significant shows were reported.

Hannigan, Lee, and Osadetz of the GSC summarized information on the two basins at the request of the province in 1994-95. Stratigraphic charts of the basins were not available.

Geology, resources Bowser basin

Initial subsidence in the Bowser basin in the Middle Jurassic allowed the organic-rich shale source rocks of the Abou formation to be deposited. The basin was then filled with arc volcanic rocks, shales, and sands of the Lower to Middle Jurassic Hazelton Group, overlain by Middle Jurassic to Cretaceous Bowser Lake Group marine and nonmarine sediments.

In the south, the Cretaceous Skeena Group marine and nonmarine sediments follow. The GSC (Hannigan et al., 1995, unpublished) sees good gas and oil potential in the Skeena Group. Predominantly nonmarine sands of the Cretaceous Sustut Group are found to the northeast, in the adjacent Sustut basin, where the GSC identifies good gas and oil potential in these sediments.

Anticlinal folding followed by several episodes of faulting has created potential structural traps. Stratigraphic traps will also exist. The GSC sees good hydrocarbon potential in structural traps in the Mid-Jurassic and Lower Cretaceous sediments in the Bowser basin.

GSC noted that the potential reservoirs in Jurassic and Cretaceous fluvial and marine clastics are sealed by shales, volcaniclastics, or tight carbonates. Source rocks include Jurassic and Cretaceous shales and some coals.

The potential oil and gas resource within the Bowser/Whitehorse area of BC has been estimated at 13.7 tcf of gas and 2.5 billion bbl of oil.

Nechako basin

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Canadian Hunter's 12 wells had TDs of 1,720-3,778 m.

Evolution of the Nechako basin is similar to that of the Bowser basin. The wells drilled through thick sequences of Tertiary, Cretaceous, and Jurassic sands, shales, conglomerates, and siltstones, often reaching TD in volcanic rocks of the Jurassic Hazelton Group, metavolcanics and metasediments of the Permian-Triassic Cache Creek Group, or Jurassic and Cretaceous granodiorites. Traces of gas were reported after attempts at completion in several zones.

The greater number of wells and seismic over this basin show that Tertiary clastics, Lower Cretaceous continental sediments, and Jurassic-Lower Cretaceous marine clastics overlie an economic basement of volcanic and igneous rocks and that the basin depth varies from 3,500 ft to over 16,000 ft. Many areas are covered by thin Upper Tertiary plateau basalts.

The GSC (Hannigan et al., 1994, unpublished) sees greatest potential for oil and gas in the Cretaceous Skeena Group sediments of the central and southern Nechako basin. They report that 90 oil shows and 10 gas shows are noted in the Skeena Group in cuttings and other well information. Source rocks are interbedded shales within the group. The traps are expected to rely on structural deformation within the basin.

A second significant play is noted where Tertiary sediments have filled extensional grabens and are overlain by thin Eocene volcanics.

The GSC defined the Nechako basin/Quesnel trough as a geologically complex sedimentary basin often complicated by a veneer of volcanic rocks on the surface. To date 12 wells have been drilled within the basin.

Exploration began in 1930 with drilling concentrating on nearby surface seeps of oil near mapped structural highs. From 1930 through to 1972 six wells were drilled without locating significant shows of oil or natural gas. In the late 1970s Canadian Hunter began a detailed exploration program that included modern seismic surveys and the drilling of six more wells from 1981-86 at a cost of more than $30 million. This program also met with limited success with only minor indications of hydrocarbons present in the wellbores.

The oil and gas resource potential of the Nechako-Chilcotin area of British Columbia has been estimated at 5.1 billion bbl of oil and 9.5 tcf of natural gas.

Coalbed methane potential

Coalbed methane resource potential is believed to exist in both the Nechako and Bowser basins.

Preliminary reserve estimates range to 16 tcf for both basins. The most significant areas of CBM are the Hat Creek area west of Kamloops in the Nechako and Telkwa coalfield at the southern end and the Groundhog coalfield at the northen extreme of the Bowser basin.

Northeast BC status

Most exploration to date has been in Northeast BC near the Alberta border, where a number of large gas plays have been developed in the WCSB.

The remaining undiscovered oil and gas resource potential for the conventional exploration area of Northeast BC is estimated at 265 million bbl of oil and 31-49 tcf of gas. Oil and gas reserves discovered to end-1998 in Northeast BC, including production, are recognized at 730 million bbl of oil and 25 tcf of gas.

British Columbia has been moving aggressively to attract more oil and gas investment and activity in the past several years. Provincial revenues from the sector increased to $660 million (Can.) in 1999 from $360 million in 1998.

The province's oil and gas sector is emerging as one of its economic mainstays. Oil and gas generates $2 billion/year in economic activity and directly and indirectly employs about 39,000 people.

Operators drilled 614 oil and gas wells and produced 25.8 bcm of gas in 1999, provincial figures show. Statistics for January through May make it clear that the number of wells drilled in 2000 will easily surpass that by a wide margin.

Miller, also the province's Minister Responsible for Northern Development, spearheads a major new initiative to encourage growth in the oil and gas industries. The initiative includes reductions in royalty rates, upgrades to northern roads needed to access services and facilities, and streamlined regulation and approval processes. The province will spend $20 million this year improving roads around Fort St. John and Fort Nelson. The initiatives are designed to double BC's oil and gas production capability by 2008.

Northern development initiatives focus generally on the area north of the road between Prince Rupert, Prince George, and the Alberta border.